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Nuclear Expert Considers Risks of Conflict with North Korea

Nuclear historian Alex Wellerstein also speaks out on nuclear terrorism, proliferation, modernization, eradication and civil defense

Alex Wellerstein, shown here in Hiroshima, August 2017: “What I find most worrying about our present time is the apparent decrease in the salience and power of the ‘nuclear taboo’ in the United States. The American public seems more willing than it ever has since the end of the Cold War to consider using nuclear weapons to achieve its policy aims.”

Alex Wellerstein

This article was published in Scientific American’s former blog network and reflects the views of the author, not necessarily those of Scientific American


For someone who thinks about doomsday for a living, Alex Wellerstein is surprisingly fun to hang out with. An historian of science who specializes in nuclear weapons, Wellerstein is my colleague at Stevens Institute of Technology. He got his Ph.D. from Harvard just seven years ago, but he has already become a go-to expert on nuclear weapons. He writes for peer-reviewed journals and his blog, Restricted Data (government secrecy is another of his passions), as well as contributing to mainstream outlets like The New Yorker, Washington Post and Radiolab. He is often quoted in others’ writings--for example, an oped in The New York Times this week. I’ve cited him a lot too. His website NUKEMAP, which lets you carry out a virtual nuclear strike on any place in the world (New York City is the number-one target), has been viewed 20 million times. He and two Stevens colleagues, political scientist Kristyn Karl and oceanographer Julie Pullen, recently got a grant from the Carnegie Corporation for the project “Reinventing Civil Defense.” Practically every time I interact with Alex, I learn something, and not just about nuclear weapons (see for example his comments on my recent post about Thomas Kuhn). I’ve been wondering what he thinks of recent tensions between the U.S. and North Korea. He is in Japan, where he just participated in a conference at Hiroshima on the anniversary of the U.S. bombing in 1945, but he took the time to answer some questions. –John Horgan

Horgan: Why the fascination with nuclear weapons?

Wellerstein: I got drawn into this topic initially for very local reasons; I was really surprised to learn about the University of California Berkeley’s long and important connections to the history of nuclear weapons, while I was a student there. It seemed so out of place, a topic drenched with irony: that the most liberal, anti-war, anti-nuclear place in the United States (for better or worse) was also one of the origins of the atomic bomb struck me as surprising.


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What kept me working on the topic through graduate school and beyond were several things. To be frank, one is the detective aspect of it: the secrecy means there are always new, strange things to find out about the topic, even though people have been talking about it and studying it for decades and decades. The other is the fact that it feels self-evidently like history that “matters”: these issues have not gone away (perhaps unfortunately), and the past gives an endless stream of insights into the present and future.

Horgan: Why did you create NUKEMAP?

Wellerstein: Some people can visualize numbers and sizes very easily from just verbose descriptions. I am not one of those people, and I suspect most people are not in that category. The original code for the NUKEMAP was written just as a means of allowing me to understand, intuitively, the scale of damage from a nuclear weapon. It’s a hard thing to wrap your head around, because it’s (fortunately) not something we’ve experienced too many times. But I found this kind of thing useful for teaching students, as well — if you look at the damage from, say, a World War II-sized nuclear weapon (20 kilotons or so) and compare it with the thermonuclear weapons of the early Cold War (10 megatons or more), it gives you some insights into why some of the Manhattan Project scientists found these to be qualitatively and even morally different weapons. That kind of distinction can be hard to make when you’re just looking at numbers.

I’ve added to NUKEMAP over time because it is a tool useful for lots of people, not just students or educators, but journalists, and just curious laymen. It doesn’t give you all of the information one might want on nuclear weapons, but it helps at least calibrate public understanding of their effects, and that goes a surprising way towards helping people talk about them.

Horgan: If Trump sought your advice on North Korea, what would you say?

Wellerstein: I think Trump in general could benefit greatly just by learning to empathize with other human beings. It appears to be a core character defect of his, and it’s a scary thing given how much of policy is about understanding consequences, and that typically requires empathy. For nuclear matters it is absolutely essential: you need to be able to understand what the other fellow is likely to do, what they are attempting to accomplish, what they will see their “options” as being.

It is clear that the North Koreans see the development of a nuclear deterrent against the United States as an existential issue. They are probably not wrong about that — the US has a reputation for causing a lot of trouble with regimes it judges as being against its interests, but it gives nuclear-armed states wide latitude. As the North Koreans have developed a mostly credible capability to threaten the cities of our allies, and maybe even our own cities, then the time of trying to imagine a non-nuclear North Korea has probably passed for the time being (maybe someday in the long future, when they feel less threatened, we can imagine such a thing). 

That doesn’t mean they are likely to attack the USA. They aren’t. They know that to do so would be suicidal. We need to make clear what conditions would result in unacceptable results for them, and they need to make clear the same for us. In both cases, there need to be options that, while not ideal, can be lived with, e.g., the North Koreans can’t think that starting a war with South Korea would be acceptable, and we shouldn’t think that we can force them to change their regime or get rid of their weapons. For deterrence to work, it requires the “alternative” to the use of weapons to be at least somewhat acceptable. This very basic idea seems not to be something Trump understands; his transactional, “deal” way of thinking doesn’t seem to allow for mutually beneficial solutions, or even mutually-good-enough solutions.

North Korea does not seem any more irrational than any other state with nuclear weapons, and we have managed to make do with fairly irrational, nuclear-armed states before (when China got the bomb in the early 1960s, it was in the middle of the Cultural Revolution, and pretty far from a stable, rational state). But if you force them into a corner, if they think that their central government is in imminent danger of “decapitation,” they may do something rash.

Horgan: What do you think of the U.S. plan, begun under Obama, to modernize its nuclear arsenal? Does it complicate nonproliferation efforts?

Wellerstein: The tricky thing about “nuclear modernization” is that if you don’t plan for some modernization then in 20-30 years you will find yourself with a broken nuclear deterrent, as the planes and ships and missiles get outside of their operational lifetimes. There are some on the anti-nuclear side, I think, who hope that ends up being the case: disarmament by mothballing. I’m not sure that’s the best approach to disarmament; one would hope it would be a little more structured, and with less chance of things breaking or going wrong.

On the other extreme, there are those who would like “nuclear modernization” to mean some kind of hyper-expensive strategic “upgrade,” to give the US some kind of new “edge” against its rivals. That seems like a new arms race at best and a waste of money at worst.

One would like to believe there is room for something in the middle, a discussion of the kind of deterrent we feel we should have if we require one, and a discussion about how to achieve that on a reasonable budget and timeline. Do we really need three “legs” of the triad (ICBMs, SLBMs, and bombers)? Do we really need over a thousand deployed warheads? (The UK, France, and China seem to feel “safe” with only a few hundred, by comparison.) Do we need an arsenal that would be “launched on warning,” as opposed to a true “second strike” capability that would only be retaliatory?

I don’t know the answer to any of these questions — and as a historian, I see my role more as understanding all sides of the debates as opposed to taking strong positions on those sides — but this seems to be the discussion we haven’t had, as a public body, and instead we are haggling over the (very expensive) price tag of upgrading our entire system. One could imagine several different approaches to this, but it seems that the underlying philosophy needs to be addressed first.

I would just also say: Obama didn’t really “begin” the modernization, these questions have been in the works since at least the second Bush administration, arguably earlier. They are a direct consequence of the end of the Cold War and the relative halting of development in the arms race. Any President several decades after the Cold War ended was going to get saddled with this question. What makes it acute with Obama is that he started his presidency with such a soaring idealism about a world without nuclear weapons, and ended it approving a massive arms spending program. I will say, my reading of history suggests this “arc” is fairly common: it is easy to be an idealist when you don’t yet have the responsibilities of the real world, and many of them end up becoming near the opposite of what they intended to be, once they are in positions of power and influence.

As for nonproliferation, the fact that the US is in possession of nearly half of the world’s nuclear weapons is going to always be brought up by countries who wonder about our commitment to nonproliferation and disarmament. The real problem with the modernization plan (and not just ours, but Russia’s as well) seems to be that it is driving a wedge between the nuclear weapons states and the non-nuclear weapons states, and that potentially endangers aspects of the non-proliferation regime (which requires fairly tight cooperation from both).

Horgan:Political scientist John Mueller and other experts have argued that the threat of nuclear terrorism has been exaggerated. What do you think?

Wellerstein: Risk is defined technically as probability of an event multiplied by the consequences of the event. In the case of nuclear terrorism we know the consequences would be quite high: tens of thousands dead, for example, and perhaps several times that number injured. Immense economic costs for rehabilitation of affected areas. And political costs that are hard to contemplate — it might make the consequences of 9/11 (vastly increased state surveillance powers and the starting of at least two foreign wars, each of which have led to further entanglements) look tame, depending on the circumstances.

So the consequences are high. I think Mueller is just wrong when he tries to minimize that aspect of things, even if the consequences are lower than maybe the “general public” might imagine (the entire world would not end, the country would not end, etc., but it would still be a disaster unparalleled in American history).

The real area of dispute is the probability. What are the odds such a thing would occur? The real pessimists think the chance is about 10% over the course of a decade or so. The optimists think the chance is maybe 0% — that it is just too hard for a non-governmental actor to acquire the necessary fissile material to make the weapon, much less turn the fuel into an actual weapon.

There are so many “missing variables” that I don’t have a lot of confidence in calculating the numbers one way or another. There are many unknowns. I don’t think the chance is 0%, however; I think that’s just too optimistic. The world contains many, many tons of fissile material, some of which is not now, or was not in the past, in extremely secure circumstances. I also have little confidence that a sophisticated terrorist organization, like al-Qaeda or ISIS, could not manifest the technical expertise necessary to turn such a fuel into a weapon if they had acquired it. It is technology that is seventy years old, is very well-documented in the public literature, and some of the weapon designs (e.g., a simple gun-type enriched uranium weapon) could be manufactured using quite generic facilities.

Nuclear terrorism is a high risk event, because of the extreme consequences. Is it a high likelihood event? I don’t know. I don’t think it’s likely to happen tomorrow, but what are its chances over the next decade? There’s a lot of factors in answering that, and we don’t (and can’t) know all of them. Is nuclear terrorism overhyped? I would challenge someone who argued that to explain what exactly the right amount of “hype” there ought to be for low-probability, high-consequence events; it smells like a classic Goldilocks problem, with no “right” answer. I would instead prefer the conversation to be somewhat re-centered: what should we be doing, policy-wise, to make the likelihood less? Are we doing enough? Are there steps we can take to mitigate the consequences? These kinds of questions strike me as more productive than trying to figure out whether the hype levels are appropriate.

Horgan: Is a global ban on nuclear weapons feasible? What are the main obstacles?

Wellerstein: Many countries recently (in July) signed a Treaty on the Prohibition of Nuclear Weapons. To nobody’s surprise, the nuclear weapons states and their allies who share their “nuclear umbrellas” did not sign it. This perhaps illustrates the main obstacle quite clearly: the nuclear weapons states still feel that nuclear weapons are necessary for their security. Should they? That’s a really hard question to answer; there are many sides to it. But suffice to say: until the states with nuclear weapons feel that they live in a world where the lack of nuclear weapons will not affect their security or their prestige, they will hold onto them tightly. And that will have rippling effects.

Horgan: What is the purpose of your new civil defense project? Are you worried defense plans might make nuclear war more “thinkable”?

Wellerstein: The Rethinking Civil Defense project that I am doing with my Stevens colleagues Kristyn Karl and Julie Pullen has two main goals. One is to think very soberly about what Civil Defense programs — that is, programs that engage the lay public in education or training about mitigating the direct consequences of a nuclear detonation, as opposed to programs that only target emergency management personnel —  should look like in the 21st century. One very basic question to ask, for example, is whether these kinds of programs would be worth the cost at all, and, if so, whether they should be coordinated by governments or other entities. What kinds of communication strategies would they use? What kinds of training? These kinds of questions.

The other goal is to use Civil Defense as a motivating idea for thinking about nuclear salience in general. Nuclear salience is what we are calling the lived experience of nuclear weapons — it is a deep awareness of nuclear detonations as being one of the threats that exist in the world today, in the same way that people who commute by car know that car accidents are something that truly exists in their world, or, say, that flu season is a real thing. The goal here is to get beyond mere “education” (with its didactic and lecturing implications) regarding the raising of nuclear “awareness,” which have been common goals in the post-Cold War to little obvious effect. Our salience-based approach is looking at the Cold War example of Civil Defense as a model; “Duck and Cover” was to nuclear weapons what school drills today are to earthquakes, tornados, and “active shooters.” So in this sense, Civil Defense might be a point of inspiration for broader thinking about cultural risk, as opposed to specific programs of operation.

As for whether I think this makes nuclear war more thinkable — I don’t think there’s much evidence of that actually being a real sentiment. An honest Civil Defense program, one which emphasizes that one is only mitigating the consequences, not preventing them, in many ways emphasizes that nuclear war is not something you would want to experience. And I would posit that the present alternative — a public that does not feel that nuclear risks are “real,” and does not appreciate their magnitude or chances realistically — is much more likely to lead people to find nuclear war “thinkable.”

Horgan: Is a nuclear attack becoming more thinkable to you? Do you think, in your gut, there will be an attack in your lifetime?

Wellerstein: What I find most worrying about our present time is the apparent decrease in the salience and power of the “nuclear taboo” in the United States. The American public seems more willing than it ever has since the end of the Cold War to consider using nuclear weapons to achieve its policy aims; read Scott Sagan and Benjamin Valentino’s recent paper on this point. The current US President seems to have no self-control, no sense of personal (much less national) consequences, and no sense of the dangers of war or even nuclear war. It is easy to imagine scenarios in which he might be convinced that a nuclear weapon might be a palatable option to use, and there are essentially no legal checks (and very few possible practical checks) on his ability to order such an attack.

It is a bad thing to have to say, but I find him much more unpredictable and disturbing along these lines than, say, Kim Jong-un, Vladimir Putin, or any of the others in the “rogue’s gallery” of people that get worried about with regards to nuclear weapons. The general know-nothing attitude of many of his key cabinet appointments (Rick Perry at the Department of Energy, for example — it appears he had no idea that most of DOE’s budget is dedicated to nuclear weapons issues when he agreed to take the job), and the constant reeling from crisis to crisis, without any sign of the long-term investment it takes to do very mundane but important things (like secure global fissile material stockpiles), makes me wonder what is slipping through the cracks.

I would like to believe that the attack on Nagasaki was the last time that nuclear weapons would be used in anger. Over a very long time horizon (say, centuries) that seems very optimistic given what we have seen so far of human beings. Is it optimistic for the next decade? For the next three years? I don’t know. I hope not.

Further Reading:

Restricted Data

Historian Contemplates "Ugly" Reality of Hiroshima and Nagasaki

Survivors of the Hiroshima and Nagasaki Bombings Speak Out on the 70th Anniversary of the Detonations.

Bethe, Teller, Trinity and the End of the Earth.

The Risks of Nuclear Weapons: An Exchange.

Are We Too Afraid of Nuclear Weapons?

We Must Start Thinking Again about the Unthinkable.

Leader of Venerable Scientific Watchdog Group Renews Focus on “Nuclear Dangers.”

Atomic Reporters Curb “Egregious” Coverage of Nuclear Perils.

How Donald Trump Can Become the Greatest Leader Ever